Heat recovery apparatus and method

ABSTRACT

A grey water heat recovery apparatus has first and second passes in counter-flow orientation. The hot side is grey water. The cold side is fresh water. It extracts heat from the grey water. The fresh water is carried in tubing bundles in series immersed in grey water sumps in cylindrical plastic, mild steel, or stainless steel pipe. Both ends of the fresh water bundle assembly extend from the same upper end pipe closure, without a pressurized line wall penetration in the walls of the pipe. There is a non-electrically conductive barrier between the fresh water and grey water flow paths. The apparatus has a leak detection circuit and co-operable bypass valves. The tube bundle is wider at the top than at the bottom. The lower manifold has grey water passages between the centering ears. The entire assembly is enclosed in a unitary external housing with easily accessible connection fittings.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation-in-Part of U.S. patent applicationSer. No. 15/910,673 filed Mar. 2, 2018, and is also aContinuation-in-part of U.S. patent application Ser. No. 14/845,737filed Sep. 4, 2015, which claims the benefit of the priority of U.S.Provisional Patent Application 62/046,570 filed Sep. 5, 2014; thespecification and drawings of all of the foregoing being incorporated intheir entirety herein by reference.

FIELD OF INVENTION

This description relates to the field of apparatus for heat recoveryfrom grey water, particularly as in residential installations.

BACKGROUND OF THE INVENTION

It is known to recover heat from grey water that would otherwise besubject to disposal. Examples of such systems are shown in WIPOpublication WO 2014/029992 of Murray, et al., and US Publication 2011/0107,512 of Gilbert.

SUMMARY OF INVENTION

The following summary precedes the more detailed discussion to follow.The summary is not intended to, and does not, limit or define theclaims.

In an aspect of the invention there is a grey water heat recoveryapparatus in which heat is transferred between a grey water stream and afresh water stream. The apparatus includes a heat exchanger that has atleast a first pass and a second pass. The first pass and second pass aremounted in series. The heat exchanger has a gravity-fed grey water flowpath, the grey water flow path including a first portion in the firstpass, and a second portion in the second pass. The grey water flow pathhas a source inlet, and a drain outlet. The grey water flow path has anintermediate portion lower than the drain outlet. The heat exchanger hasa pressure-fed fresh water flow path. The fresh water flow path issegregated from the grey water flow path. The fresh water flow path hasa counter-flow orientation relative to the grey water flow path. Thefresh water flow path of the heat exchanger is at least predominantlyimmersed in the grey water flow path. The fresh water flow path has afresh water source and a fresh water outlet, both the fresh water sourceand the fresh water outlet is positioned at respective heights higherthan the drain outlet of the grey water flow path. The heat exchanger isfree of fresh water wall penetrations of the grey water flow path lowerthan the drain outlet of the grey water flow path.

In a feature of that aspect of the invention, the first pass and thesecond pass are of substantially the same size and are mountedside-by-side. In another feature, the heat exchanger has more than twopasses, and the more than two passes are mounted in a side-by-sidebundle. In yet another feature, the first pass includes a first shelldefining an outer wall of a first portion of the grey water flow path;the second pass includes a second shell defining an outer wall of asecond portion of the grey water flow path; the fresh water flow pathincludes a first portion and a second portion; the first portion of thefresh water flow path is nested within the first shell; and the secondportion of the fresh water flow path is nested within the second shell.In a further feature, the first shell has a resting sump fluid level,and the first portion of the fresh water flow path has an entrance toand an exit from the first shell, both of the entrance and the exit isat a level at least as high as the resting sump fluid level. In anotherfeature, the first shell has at least one plug fitting; the firstportion of the fresh water flow path has an entrance to and an exit fromthe first shell; both of the entrance and the exit is carried through aplug fitting of the at least one plug fittings. In still anotherfeature, the first shell is made from a cylindrical pipe; thecylindrical pipe has a first end and a second end; the cylindrical pipehas at least a first plug fitting; the first plug fitting mates with thefirst end of the cylindrical pipe; the first portion of the fresh waterflow path has an entrance and an exit; and the entrance and the exit ofthe fresh water flow path are mounted through the first plug fitting.

In another feature, the first pass includes a first plastic cylindricalpipe defining an outer wall of a first portion of the grey water flowpath. The second pass includes a second plastic cylindrical pipedefining an outer wall of a second portion of the grey water flow path.The fresh water flow path includes a first portion and a second portion.The first portion of the fresh water flow path includes a first coilnested within the first shell. The second portion of the fresh waterflow path includes a second coil nested within the second shell. Thesecond coil has a fresh-water connection fitting. The first and secondcoils are connected in series. The first and second coils are made ofmetal, e.g., copper or stainless steel.

In a further feature, each of the first and second coils is a coppercoil. Each of the first and second cylindrical plastic pipes ispredominantly upstanding. Each of the first and second plastic pipes hasa bottom end closure. Each of the first and second plastic pipes has atop end closure. Each of the first and second coils has a return leg,whereby each of the first portion and the second portion of the freshwater flow path has first and second terminations, and the first andsecond terminations pass through the top end closure of the first andsecond cylindrical plastic pipes, respectively. The top end closures ofthe first and second cylindrical plastic pipes is higher than the drainoutlet of the grey water flow path. The first and second cylindricalplastic pipes and the first and second coils extending downwardly of thedrain outlet whereby the cylindrical plastic pipes define first andsecond sump portions, and the first and second coils are predominantlysubmerged in the first and second sump portions. In still anotherfeature, there is, in combination, the heat recovery apparatus and awater heater. The fresh water flow path of the grey water heat recoveryapparatus is upstream of the water heater. The water heater has supplyconduits to at least a first hot water load, and the grey water flowpath of the heat recovery apparatus receives grey water from at leastthe first hot water load.

In another feature, the apparatus includes a space filling memberpositioned to reduce flow path area of the grey water. In a furtherfeature, the apparatus includes at least one return. The return ismounted within an obstructing member. The grey water is restricted toflow in an annular region outside the obstructing member. In anotherfeature, the apparatus includes a tube bundle. The tube bundle has anoutlet and an inlet. Both the outlet and the inlet are located at oneend of the tube bundle whereby the tube bundle may be extracted from oneend of the apparatus as a single modular unit. In an additional furtherfeature, the tube bundle includes an inlet header, a return header, anarray of feeder tubes extending between the inlet and return headers,and a return. The inlet header is mounted concentrically about thereturn, said return passing though said inlet header.

In another aspect of the invention, there is a grey water heat recoveryapparatus in which to transfer heat between a grey water stream and afresh water stream. The grey water heat recovery apparatus has a heatexchanger that has a first pass and a second pass, the first pass andthe second pass is connected in series. The heat exchanger has a firstside defining a grey water flow path, and a second side defining afresh-water flow path. The grey water and fresh water paths aresegregated from each other. The grey water flow path is a gravity-feedflow path. The fresh water flow path is a pressure-feed flow path. Theheat exchanger has a grey water flow path inlet and a grey water flowpath outlet. At least a portion of one of the first pass and the secondpass is lower than the grey water flow outlet whereby the heat exchangerdefines at least a first grey water sump. At least one of the first passand the second pass including a first cylindrical pipe member throughwhich to conduct the grey water stream, the first cylindrical pipemember defining a containment wall of at least a portion of the greywater flow path. The first cylindrical pipe member has a grey waterinlet and a grey water outlet. The first cylindrical pipe member has afirst end, and a first end member, the first end member defining aclosure of the first end of the first cylindrical pipe member. A firstfresh water flow element is nested within the first cylindrical pipemember. The first fresh water flow element extends axially within thefirst cylindrical pipe member. The first fresh water flow element has aninlet and an outlet. Both the fresh water inlet and the fresh wateroutlet are mounted to pass through the first end member of the firstcylindrical pipe member.

In a feature of that aspect of the invention, the first fresh water flowelement includes a metal coil. The metal coil has a return leg. Thefresh water flow element has first and second end connections. Both ofthe first and second end connections of the metal coil pass through thefirst end of the first cylindrical pipe member. In another feature, thefirst and second cylindrical pipe members are mounted togetherside-by-side, and are mounted adjacent to a water heater. The waterheater has an overall height, and the heat recovery apparatus has anoverall height. The overall height of the heat recovery apparatus is inthe range of 2/3 to 3/2 of the height of the water heater. In a furtherfeature, one of: (a) the first pass and the second pass are connected todefine a single grey water sump in which the grey water outlet of thefirst pass is connected to a lower portion grey water entry of thesecond pass; and (b) the first pass and the second pass are connected todefine a first grey water sump in the first pass and a second grey watersump in the second pass, in which the outlet of the first sump iscarried to a top portion entry into the second sump. In another feature,there is the heat recovery apparatus in combination with a water heater.The grey water heat recovery apparatus is connected as a fresh waterpre-heater for the water heater.

In another aspect of the invention there is a grey water heat recoveryheat exchanger. It has a first cylindrical plastic pipe for grey waterwith a first metal coil for fresh water nested therein. It also has asecond cylindrical plastic pipe for grey water with a second metal coilfor fresh water nested therein. The first cylindrical plastic pipe hasan inlet for grey water. The second cylindrical plastic pipe has anoutlet for grey water. The first and second cylindrical plastic pipesare connected in series to conduct grey water from the first cylindricalplastic pipe to the second cylindrical plastic pipe. The first metalcoil is connected in series with the second metal coil. The second metalcoil has a fresh water inlet. The first metal coil has a fresh wateroutlet. The fresh water coils are mounted for counter-flow operationrelative to the grey water conducting first and second cylindricalplastic pipes. At least one of the first and second cylindrical plasticpipes defining at least a portion of a grey water sump in which at leasta portion of the first and second metal coils is mounted.

In a feature of that aspect of the invention, at least one of the firstand second cylindrical plastic pipes has a first end closure, and thecorresponding one of the first and second coils has first and second endportions that pass through the first end closure. In another feature,the first and second cylindrical plastic pipes are in a predominantlyupstanding orientation, and the grey water outlet of the secondcylindrical plastic pipe is higher than a predominant portion of atleast one of the first and second fresh water coils. In still anotherfeature, the first and second cylindrical plastic pipes stand on acommon base and are mounted together in a single mounting with both ofthe first and second cylindrical plastic pipes is in an upstandingorientation. The first cylindrical plastic pipe has a first end and asecond end. The first end is higher than the second end. The second endof the first cylindrical plastic pipe has a blind closure. The first endof the first cylindrical plastic pipe has a closure has first and secondpenetrations through which pass respective first and second ends of thefirst fresh water coil. The first and second penetrations are higherthan the grey water outlet of the second cylindrical plastic pipe. Thefirst fresh water coil has a helical coil portion and a return legportion. The helical coil has an outside diameter fitting within thefirst cylindrical plastic pipe to permit construction of the heatexchanger by axial insertion of the helical coil into the firstcylindrical plastic pipe. The second cylindrical plastic pipe has afirst end and a second end. The first end is higher than the second end.The second end of the second cylindrical plastic pipe has a blindclosure. The first end of the second cylindrical plastic pipe has aclosure has first and second penetrations through which pass respectivefirst and second ends of the second fresh water coil. The first andsecond penetrations are higher than the grey water outlet of the secondcylindrical plastic pipe. The second fresh water coil has a helical coilportion and a return leg portion. The helical coil has an outsidediameter fitting within the second cylindrical plastic pipe to permitconstruction of the heat exchanger by axial insertion of the helicalcoil into the second cylindrical plastic pipe.

In another feature, there is the grey water heat recovery assembly incombination with a grey water drainage system, a water heater, and a hotwater distribution system. The fresh water inlet of the heat exchangeris connected to a fresh water supply system downstream of a water meter.The fresh water outlet of the heat exchanger is connected to an inlet ofthe water heater. The water heater has an outlet connected to supplywater to at least one of a hot water tap, a shower, a bath-tub, aclothes washer, and a dishwasher. The grey water drainage system isconnected to a drain of at least one of a sink; a shower, a bath-tub, aclothes washer, and a dishwasher. The grey water drainage system issegregated from any sewage water system. The grey water drainage systemis connected to the grey water inlet of the first cylindrical plasticpipe. The grey water drainage system includes an overflow bypass of theheat exchanger. There is a grey water inlet filter mounted to interceptobjects in the grey water carried by the grey water drainage system tothe heat exchanger. The outlet of the second cylindrical plastic pipedrains into a sewage drain.

In another feature of any of the foregoing aspects, the apparatus isenclosed in a unitary cylindrical housing in which both of the first andsecond (and any other) stages are enclosed. Externally accessible greywater and fresh water connection fittings pass through the externalcylindrical housing. The fresh water connection fitting extends througha top end of the cylindrical housing. The grey water connection fittingsextend through a sidewall of the cylindrical housing.

In another aspect of the invention, there is a grey water heat recoveryapparatus. It has a heat exchanger having at least a first pass and asecond pass, the first pass and second pass being mounted in series. Theheat exchanger has a gravity-fed grey water flow path, the grey waterflow path including a first portion in the first pass, and a secondportion in the second pass, the first portion in the first pass beingupstream of the second portion in the second pass, the grey water flowpath having a source inlet, and a drain outlet. The grey water flow pathhas an intermediate portion lower than the drain outlet. The heatexchanger has a pressure-fed fresh water flow path, the fresh water flowpath being segregated from the grey water flow path. The fresh waterflow path has a first portion in the second pass, and a second portionin the first pass, the second portion of the fresh water flow path beingdownstream of the first portion of the fresh water flow path. The freshwater flow path of the heat exchanger is at least predominantly immersedin the grey water flow path. The fresh water flow path has a fresh watersource and a fresh water outlet, both the fresh water source and thefresh water outlet being positioned at respective heights higher thanthe drain outlet of the grey water flow path. The heat exchanger is freeof fresh water wall penetrations of the grey water flow path lower thanthe drain outlet of the grey water flow path. There is anon-electrically conductive barrier between the grey water flow path andthe fresh water flow path.

In a feature of that aspect of the invention the apparatus includes aleak detection circuit. In another feature, the leak detection circuitincludes at least a first terminal mounted in the fresh water flow path,and at least a second terminal mounted in the grey water flow path. Theleak detection circuit senses at least one of (a) resistance; and (b)voltage potential between the fresh water flow path and the grey waterflow path. In another feature, the leak detection circuit includes astorage member operable to provide power independently of theavailability of external power.

In still another feature, the leak detection circuit is operable toadjust the flow of at least one of (a) grey water in the grey waterpath; and (b) fresh water in the fresh water path.

In another feature, the apparatus includes a fresh water bypass, andflow through the fresh water bypass is controlled in response tooperation of the leak detection circuit. In still another feature, theapparatus includes a grey water bypass, and flow through the grey waterbypass is controlled in response to the leak detection circuit.

In another feature, the first pass and the second pass are ofsubstantially the same size and are mounted side-by-side. The first passincludes a first shell defining an outer wall of a first portion of thegrey water flow path. The second pass includes a second shell definingan outer wall of a second portion of the grey water flow path. The firstportion of the fresh water flow path is nested within the second shell.The second portion of the fresh water flow path is nested within thefirst shell. The first shell has a resting sump fluid level, and thesecond portion of the fresh water flow path has an entrance to and anexit from the first shell, both of the entrance and the exit being at alevel at least as high as the resting sump fluid level. The first shellhas at least a first closure fitting; the second portion of the freshwater flow path has an entrance to and an exit from the first shell;both of the entrance and the exit being carried through the firstclosure fitting.

In another feature, the apparatus includes a leak detection circuit. Theleak detection circuit includes at least a first terminal mounted in thefresh water flow path, and at least a second terminal mounted in thegrey water flow path lower than a resting water level therein.

The leak detection circuit is sensitive to a change in resistancebetween the fresh water flow path and the grey water flow path. The leakdetection circuit includes a storage member operable to provide powerindependently of the availability of external power. The leak detectioncircuit is operable to adjust the flow of at least one of (a) grey waterin the grey water path; and (b) fresh water in the fresh water path. Theapparatus includes a fresh water bypass, and flow through the freshwater bypass is controlled in response to operation of the leakdetection circuit. The apparatus includes a grey water bypass, and flowthrough the grey water bypass is controlled in response to the leakdetection circuit. The leak detection circuit is operable to measureresistance between the first terminal and the second terminal. The leakdetection circuit is operable to govern a fresh water bypass valve; anda grey water bypass valve. In a first mode of operation the fresh waterbypass valve is closed and the fresh water flow path is open; and thegrey water bypass valve is closed and the grey water flow path is open.In a second mode of operation the fresh water bypass valve is open andthe fresh water flow path is closed, and the grey water bypass valvebeing open.

In another feature, the first pass includes a first plastic cylindricalpipe defining an outer wall of a first portion of the grey water flowpath, the outer wall being thermally insulated. The second pass includesa second plastic cylindrical pipe defining an outer wall of a secondportion of the grey water flow path the outer wall being thermallyinsulated. The second portion of the fresh water flow path includes afirst tube bundle nested within the first shell. The first portion ofthe fresh water flow path includes a second tube bundle nested withinthe second shell. The second tube bundle has a fresh-water sourceconnection fitting. The second tube bundle is connected in series to thefirst tube bundle. The first and second tube bundles being made ofmetal. Each of the first and second cylindrical plastic pipes ispredominantly upstanding. Each of the first and second plastic pipes hasa bottom end closure. Each of the first and second plastic pipes has atop end closure. Each of the first and second tubes bundles has acounter-direction leg, whereby each of the first portion and the secondportion of the fresh water flow path has first and second terminations,and the first and second terminations pass through the top end closureof the first and second cylindrical plastic pipes, respectively. The topend closures of the first and second cylindrical plastic pipes beinghigher than the drain outlet of the grey water flow path. The first andsecond cylindrical plastic pipes and the first and second tube bundlesextending downwardly of the drain outlet whereby the cylindrical plasticpipes define first and second sump portions, and the first and secondtube bundles are predominantly submerged in the second and first sumpportions. The apparatus includes a leak detection circuit. At least oneof the tube bundles has a first terminal of the leak detection circuitmounted in the fresh water path therein. The grey water path includes atleast a second terminal of the leak detection circuit mounted thereinlower than a resting water level thereof. The leak detection circuit isoperable to measure resistance between the first terminal and the secondterminal. The leak detection circuit is operable to govern a fresh waterbypass valve; and a grey water bypass valve. In a first mode ofoperation the fresh water bypass valve and the grey water bypass valveis closed. In a second mode of operation the fresh water bypass valveand the grey water bypass valve are open. In another feature, theapparatus is circumscribed by an external housing in which both of thefirst and second stages are enclosed, with grey water and fresh waterconnection fittings being externally accessible.

In still another feature, the grey water heat recovery apparatus iscombined with a water heater, a leak detection circuit and a fresh waterbypass. The fresh water flow path of the grey water heat recoveryapparatus is upstream of the water heater. The water heater has supplyconduits to at least a first hot water load. The grey water flow path ofthe heat recovery apparatus of claim 1 is mounted to receive grey waterfrom at least the first hot water load; and the leak detection circuitis connected to direct fresh water through the fresh water bypass to thewater heater and to shut off fresh water flow through the fresh waterflow path in response to leak detection.

In another aspect of the invention, there is a grey water heat recoveryapparatus. It has at least a first heat exchanger pass has an externalshell and a tube bundle. The external shell is formed of a cylindricalplastic pipe. The cylindrical plastic pipe has a first end and a secondend. In operation, the first end is located higher than the second end.The second end is blocked to form a sump within the cylindrical plasticpipe. The cylindrical plastic pipe has a first port and a second port.The first port is nearer the first end than is the second port. Thefirst port defines a resting water level when gray water is contained inthe sump. One of the first and second ports defines an inlet for greywater to the cylindrical plastic pipe, the other of the first and secondports defines an outlet for grey water from the cylindrical plasticpipe. The cylindrical plastic pipe defines a flow path for grey waterbetween the inlet and the outlet thereof. The first end of thecylindrical plastic pipe provides an entrance or entry. The tube bundleis sized to fit within the entry at the first end of the plastic pipe.The tube bundle is axially slidable within the external shell oninstallation. The tube bundle has a first end and a second end. The tubebundle has a first manifold at the first end thereof, and a secondmanifold at the second end thereof. The tube bundle includes a returnpassing through the first manifold and extending to the second manifold.The first manifold and the second manifold fit within the cylindricalplastic pipe. As installed, the second end of the tube bundle is closerto the second end of the cylindrical plastic pipe than is the first endof the tube bundle. The tube bundle has an inlet and an outlet, the tubebundle defines a fresh water flow path between the inlet and outletthereof. Both the inlet and the outlet of the tube bundle is located atthe first end of the tube bundle. As installed in the cylindricalplastic pipe, the inlet and the outlet of the tube bundle is accessibleat the first end of the cylindrical plastic pipe at a level higher thanthe resting water level of the cylindrical plastic pipe.

In a feature of that aspect, the cylindrical plastic pipe has at leastone of (a) an inside diameter less than 8 inches; and (b) a length todiameter ratio of greater than 8:1. In another feature, the apparatushas at least a first and a second heat recovery apparatus mountedside-by-side and joined together in fluid communication in series. In anadditional feature, at least the first and second heat recoveryapparatus are mounted together within a single housing. In a furtherfeature, the tube bundle includes a set of helical coils extendingaround the return. In a still further feature, the second end of thecylindrical plastic pipe has a valve mounted thereat, and the valve isoperable to permit flushing of the sump. In still another feature, theapparatus includes a leak detector. In yet another feature, the returnis at least partially insulated. In a still further feature, the tubebundle includes an array of pipes spaced about the return pipe. Thearray of pipes extends between, and is in fluid communication with, thefirst manifold and the second manifold. The array of pipes has a tighterfootprint at the second manifold than at the first manifold. In anotherfeature, the second manifold has a smaller outside wall diameter thandoes the first manifold.

In still another aspect, there is a grey water heat recovery apparatus.It has a cylindrical plastic pipe and a tube bundle that inserts axiallywithin the cylindrical plastic pipe. The tube bundle has a firstmanifold, a second manifold, a return pipe, and a pipe array. The returnpipe is in fluid communication with the second manifold and passingupwardly through the first manifold to terminate at a first pipeconnection. The pipe array extends between, and is in fluidcommunication with both the first manifold and the second manifold. Thefirst manifold has a second pipe connection extending upwardlytherefrom, the second pipe connection is in fluid communication with thefirst manifold. At least one of (a) the pipe array has a smallerconnection footprint with the second manifold than with the firstmanifold; and (b) the second manifold has a peripherally extending wall,the first manifold has a peripheral wall, and the peripheral wall of thesecond manifold has a shorter periphery than has the peripheral wall ofthe first manifold.

In a feature of that aspect, the pipe array has a smaller connectionfootprint with the second manifold than with the first manifold. Inanother feature, the second manifold has a peripherally extending wall,the first manifold has a peripheral wall, and the peripheral wall of thesecond manifold has a shorter periphery than has the peripheral wall ofthe first manifold. In another feature, the pipe array includes at leasta first pipe that has a straight portion extending axially from thefirst manifold, and a bent portion extending from the straight portiontoward the second manifold. In still another feature, the straightportion is more than twice the length of the bent portion. In anotherfeature, the peripheral wall of the first manifold has a first diameter.In another feature, the peripheral wall of the second manifold has asecond diameter. The second diameter is smaller than the first diameter.In another feature, the second manifold has a set of centering earsextending radially outwardly thereof. In a further additional feature, agrey water flow path is defined outwardly of the second manifold,inwardly of the cylindrical plastic pipe, and sectorally between anadjacent pair of the centering ears. In still another feature, the pipearray has a total cross-sectional flow area that is at least as great asthe cross-sectional flow area of the return pipe.

BRIEF DESCRIPTION OF THE ILLUSTRATIONS

These and other features and aspects of the invention may be explainedand understood with the aid of the accompanying illustrations, in which:

FIG. 1 is a conceptual schematic view of a building, such as aresidence, having grey water sources;

FIG. 2 is a cross-sectional view of an example of a heat exchangerarrangement according to an aspect of the invention;

FIG. 3 is a cross-sectional view of an alternate embodiment of heatexchanger arrangement to that of FIG. 2;

FIG. 4 is a cross-sectional view of a cap assembly of the heat exchangerarrangement of FIG. 2;

FIG. 5 is an alternate arrangement to that of FIG. 2;

FIG. 6 is an alternate arrangement to that of FIG. 3;

FIG. 7 shows a partial view in section of a double-helical alternatearrangement to that of FIG. 2;

FIG. 8 shows a section, looking downward at the level of the upperoutlet of one of the passes of a two-stage embodiment of heat exchangersuch as in FIG. 2;

FIG. 9 shows a sectional view, analogous to the view of FIG. 8, lookingdownward, through a three-stage embodiment of heat exchanger;

FIG. 10a is a view of an alternate embodiment of a heat exchangerapparatus to that of FIG. 2;

FIG. 10b is a further view of the embodiment of FIG. 10, sectioned toshow details within the heat exchange coils;

FIG. 11a shows a further alternative embodiment to that of FIG. 2;

FIG. 11b shows an enlarged fore-shortened sectional detail of theembodiment of FIG. 11 a;

FIG. 11c is a sectional view of a manifold of the embodiment of FIG. 11a; and

FIG. 11d is a side view of a heat exchange bundle module of theembodiment of FIG. 11 a;

FIG. 12a is a side view of an alternate embodiment to that of FIG. 2;

FIG. 12b is a sectioned, vertically foreshortened view of the embodimentof FIG. 12 a;

FIG. 12c is a sectioned view looking downward and showing the pipearrangement of the embodiment of FIG. 12 a;

FIG. 12d shows a top view of the embodiment of FIG. 12 a;

FIG. 12e shows a double-wall section of the embodiment of apparatus ofFIG. 12a showing internal fluting;

FIG. 13 shows a vertically foreshortened cross-section of a furtheralternative embodiment to that if FIG. 12 a;

FIG. 14a shows an alternate embodiment of the apparatus of FIGS. 11a and11 b;

FIG. 14b shows a vertically foreshortened cross-section of the apparatusof

FIG. 14a comparable to the view of FIG. 11 d;

FIG. 15a is a front view of an alternate tube bundle heat exchangerassembly to that of FIG. 11 d;

FIG. 15b is a central cross-sectional view of the tube bundle of FIG.15a taken on section ‘15 b-15 b’ of FIG. 15 a;

FIG. 15c is an enlarged detail of the upper or top end of the tubebundle of

FIG. 15b showing a cross-section of the upper manifold thereof;

FIG. 15d is an enlarged detail of the lower or bottom end of the tubebundle of FIG. 15b showing a cross-section of the bottom manifoldthereof; and

FIG. 15e is a cross-sectional view of the tube bundle of FIG. 15alooking upward on section ‘15 e-15 e’ of FIG. 15 a;

FIG. 15f is a cross-sectional view of the tube bundle of FIG. 15alooking downward on section ‘15 f-15 f’ of FIG. 15a ; and

FIG. 15g is a general overall perspective view of the tube bundle ofFIG. 15a , foreshortened at a mid-length section.

DETAILED DESCRIPTION

The description that follows, and the embodiments described therein, areprovided by way of illustration of an example, or examples, ofparticular embodiments incorporating one or more of the principles,aspects and features of the invention. These examples are provided forthe purposes of explanation, and not of limitation, of those principles,aspects and features. In the description, like parts are markedthroughout the specification and the drawings with the same respectivereference numerals. The drawings may be taken as being to scale, orgenerally proportionate, unless indicated otherwise. In thecross-sections, the relative thicknesses of the materials may not be toscale.

The scope of the invention herein is defined by the claims. Though theclaims are supported by the description, they are not limited to anyparticular example or embodiment. Other than as indicated in the claims,the claims are not limited to apparatus or processes having all of thefeatures of any one apparatus or process described below, or to featurescommon to multiple or all of the apparatus described below. It ispossible that an apparatus, feature, or process described below is notan embodiment of any claimed invention.

The terminology used in this specification is thought to be consistentwith the customary and ordinary meanings of those terms as they would beunderstood by a person of ordinary skill in the art in North America.The Applicant expressly excludes all interpretations of terminology thatare inconsistent with this specification, and, in particular, expresslyexcludes interpretation of the claims or the language used in thisspecification such as may be made in the USPTO, or in any other PatentOffice, other than those interpretations for which express support canbe demonstrated in this specification or in objective evidence ofrecord, demonstrating how the terms are used and understood by personsof ordinary skill in the art generally, or by way of expert evidence ofa person of experience in the art.

In this discussion it may be helpful to make reference to a gravitybased co-ordinate system. That is, in flow systems generally, there is asource or inlet of flow, and an outlet or discharge of flow. Fluid movesfrom a location of higher pressure or potential to a location of lowerpressure or potential. In a fresh water supply system, the source ofpressure may be a pump or an accumulator, such as a water tower, thatmay be used to provide or maintain a desired system head or pressure. Adrain system, whether for sewage or for grey water, may be a gravity fedor gravity driven system in which the head of the flow, if any, isdetermined by the height of the water column of the drain. Such a systemmay be considered a low, or very low, head system. In either case, thesystem will have an upstream direction from which flow originates, and adownstream direction toward which flow occurs. In the context of thepresent description, gravity flow systems also include septic or othersystems where the material that collects in the drainage system underthe influence of gravity is then pumped out, such as, for example, to aholding tank or to a septic bed. The drainage system upstream of theseptic pump is a gravity flow system within the meaning herein, eventhough there may be provision to pump out the downstream end orcollector, or sump of the system. In such systems, there may be aseparate grey water sump and grey water pump to raise the effluent to alevel to reach the holding tank or to flow into the septic bed, as maybe.

In this description there are cylindrical objects. In such circumstancesit may be appropriate to consider a cylindrical polar co-ordinate systemin which the axis of rotation of the body of rotation, or cylinder, asmay be, may be considered the axial or x-direction. The perpendiculardistance from the x-axis is defined as the radial direction or r-axis,and the angular displacement is the circumferential direction, in whichangular distance may be measured as an angle of arc from a datum. Thecommonly used engineering terms “proud”, “flush” and “shy” may be usedherein to denote items that, respectively, protrude beyond an adjacentelement, are level with an adjacent element, or do not extend as far asan adjacent element, the terms corresponding conceptually to theconditions of “greater than”, “equal to” and “less than”.

Considering FIGS. 1 and 2, there is a building 20. Building 20 may be aresidential dwelling, whether a single family home, or multiple unitresidence, as may be. It may be a school or office building. However itmay be, building 20 may have a water supply system 22, and a drainsystem 24. Water supply system 22 may include a fresh, cold water supplysystem, 21, and a fresh hot water supply system 23, such as may be fedfrom a water heater. Drain system 24 may include a septic or sewersystem 26, and may include a grey water system 28. Grey water system 28is segregated from septic or sewer system 26. Septic or sewer system 26may be connected to toilets and utility room floor drains, for example,and may have drainage runs, or pipes, that collect at a common manifold,or drain, or riser or stack, indicated generally as 30. In either case,building 20 may have a mechanical or utility room, typically in abasement, or at foundation level.

Grey water system 28 may include one or more sink drains, whether from awashroom sink, or from a kitchen sink, or laundry tub, genericallyindicated as sink 32; from one or more shower drains, indicatedgenerically as 34; from a kitchen sink or dishwasher drain, indicatedgenerically as 36. These drains connect to a common grey water drainline or manifold, such as may be indicated as 38. Manifold 38 feeds aheat recovery apparatus 40. That is, the gravity driven grey wateroutput or discharge flow of manifold 38 is the grey water input flow ofheat recovery apparatus 40.

In the example of FIG. 2, heat recovery apparatus 40 may include anoverflow bypass 42 that is connected to conduct flow arriving frommanifold 38 to the main drain 50 in the event that some or all of thegrey water input flow does not flow into the heat exchange components ofapparatus 40, for whatever reason. Heat recovery apparatus 40 may alsoinclude an input filter, or filters, indicated as 44, to exclude solidparticles or other objects whose presence or accumulation within theheat exchange elements of apparatus 40 may not be desired. The inletfilter may be placed so that the inflow into unit 40 passes partially orpredominantly upward, whereby objects that might otherwise tend toaccumulate on the filter element may, when the flow relents or ceases,tend to fall downward, or settle, under the influence of gravity andcollect in a cleanout, such as suggested at 46, and such as may beemptied from time to time by an operator as a part of maintenance. Theelement, or elements, of filter 44 may also be removed, cleaned, orreplaced from time to time. Ordinary flushing of cleanout 46 may becontrolled by a valve 76 mounted to the cleanout sump drain outlet. Theoutput of valve 76 leads to main drain 50. Main drain 50 carrieseffluent below the level of the foundation, or basement floor 55, eitherto the municipal sewers, or to a septic tank or bed, with or without anintervening pump-out pump as may be.

In the example of FIG. 2, heat recovery apparatus 40 includes a firststage, or pass, 52, and a second stage or pass, 54. Heat recoveryapparatus 40 may be considered as a heat exchanger (or series ofconnected heat exchangers), in which each pass 52 or 54 (or more, as maybe) is itself a heat exchanger. The stages or passes are connected inseries, and in the embodiments of FIGS. 2 and 3 the inputs and outputson the hot and cold sides, respectively, are connected in oppositedirections, such that heat recovery apparatus 40 is a counter-flow heatexchanger.

In FIG. 2, following the grey water, which is presumed to be the hotside flow (that is, the incoming grey water is assumed to be warmer thanthe incoming fresh water supply), main grey water drain line 38 arrivesat a tee 56 to which overflow bypass 42 is connected. Thestraight-through output line defines the infeed pipe 58 to first pass52. It is connected to bottom union 60 at an elbow 62 that is teed intofirst pass 52 below filter 44. The main body of first pass 52 may beformed of a round cylindrical pipe 64 that defines the outer shell ofthe unit. Pipe 64 may be made of any suitable drain piping material, andmay, if desired, be externally insulated. In one example pipe 64 may bePVC or ABS or metal pipe. Pipe 64 may tend to have a length that is anorder of magnitude, or more, greater than its diameter. In one examplepipe 64 may be an ABS pipe of nominal 4 inches in diameter (i.e., theinside wall defines a 4 inch (roughly 10 cm) diameter passageway). Othersizes may be used. In one embodiment the pipe may have a nominal 6″(roughly 15 cm) internal diameter. Infeed pipe 58 (and all of the othergrey water piping discussed herein) may likewise be any kind of pipesuitable for drain installations, and may typically be a plastic orreinforced plastic pipe, be it ABS, PVC or some other. To the extentthat heat transfer through the outer wall is not desired, pipe 64 maytend not to be made of copper, or may be externally insulated, or both.The bottom end of pipe 64 is closed off. In the embodiment shown, theend closure fitting of the closed end is closed by a valve 76. Valve 76may be opened when it is desired to flush out the clean out at thebottom of the sump. In normal operation valve 76 will be closed. At thefar end of pipe 64 there is an off-take or outlet, which may be a tap ortee in the sidewall as at 66, defining the grey-water outlet ordischarge of first pass 52. The uppermost end, pipe 64 is closed byanother end closure or end closure fitting such as a cap or plugfitting, 70, shown in cross-section in FIG. 4, and described in greaterdetail below.

A transfer tube or pipe 72 extends from outlet 66 of first stage 52 tothe inlet of second stage 54. Again, the inlet pipe is teed into thebase of second stage 54 at the bottom, or lower portion, where there isa flushing or clean-out drain 74 controlled by a valve 76. Second stage54 similarly has a main body that may be formed of a cylindrical pipe78, typically of the same diameter and material as that of first stage52, with an outlet or off-take, or discharge as at 80, and an end plugor cap or on end closure or end closure fitting as at 82. The outlet ordischarge of second stage 54, being the outlet of grey water from heatrecovery apparatus 40 more generally, is connected to drain into maindrain 50. That is, the grey water and septic water systems aresegregated upstream, but drain into a common flow at the outletjuncture, at 84. The grey water path may be considered to be the hotside, or hot path, of the heat exchanger, from which heat is extracted.

The other side of the heat exchanger, typically termed the cold side orcold path, is designated generally as 90. It is the side of the heatexchanger to which heat is transferred or rejected. The cold side maytypically provide a flow for inlet water under pressure, typically 30-50psig of a municipal fresh water supply. Inasmuch as the fresh water maytypically enter from buried pipe, the cold water temperature may oftenbe in the range of 40-50 F. The cold water pipe, being a pipe underpressure, may typically be a copper pipe, although stainless steel orany other suitable pressure line pipe may also be used.

The cold water supply, after having passed through the water meter, mayhave a tee at which one side is directed to the cold water outlets inthe building, and another side through which fresh water flow isdirected to the hot water distribution. As shown in FIG. 2, the hotwater heater distribution feeder line 88 enters the second pass at aninlet 92 in cap or plug 82. The cold water supply may then have a heatexchange element 94 that is mounted to plug 82. The element may havemany different forms, and may include finned heat exchange members.However, as shown, element 94 may have the form of a coil. The coil mayhave more than one pipe, and may include twinned pipes coiled in anaxially side-by-side helix of nested helices, as in the embodiment ofFIGS. 10a and 10b , for example, or in nested helices of differentradii. The coils may not be circular in cross-section, but may beflattened or oval, to form a more ribbon-like section having smallerhydraulic diameter than a circular section. The coil may be a singlecoil of copper pipe of constant diameter and circular section, coiled ona constant radius and having regular axial pitch between the turns ofthe coil. At the lower end of the coil, the run in the other direction,such as may be called the “return” leg, may be a straight leg runningaxially or predominantly axially relative to cylindrical pipe 78, andmay be a substantially straight leg 96, that also passes through cap orplug 82 to its end or termination, or outlet connection, be it acoupling, union, adapter, or other pipe fitting. The return leg 96 mayrun within the helix of the coiled portion, and need not be centered inthe coil, but may be offset from center. The straight leg portion may bereferred to as the “return” leg, although the flow may be in theopposite direction according to the manner of connecting the inlet andoutlet pipe connections of element 94 (or element 102 as below). The useof the “return” terminology in this sense is intended not as anindication of internal flow direction, but rather of providing a line ofshorter path length back to roughly the same entrance location as theother, coiled leg, whichever of the two may be the ‘inlet” or “outlet”.To avoid confusion, the term “counter-direction leg” may be used inplace of “return leg”. The use and installation of such fittings arethought to be well understood by persons of skill in the art. It isassumed in this description that heat transfer between the fresh waterand the grey water occurs predominantly in the coiled portion of thecoil, 94, rather than in the straight leg 96.

The cold water pipe leaving second stage 54 then passes through atransfer tube or pipe 100 to first pass or stage 52. The fresh waterheat exchange element 102 in first pass 52 may be different from that insecond pass 54, in the general case, but may typically be the same asheat exchange element 94, and may be a helical copper coil. Again, heatexchange element 102 may have a coiled portion 101, and a straight legportion 103. The straight leg portion may be referred to as the returnleg, although the flow may be in the opposite direction according to themanner of connecting the inlet and outlet pipe connections of element102 (or element 94 as above). Again, it is thought that heat transferoccurs predominantly between the coiled portion 101 and the grey water,much more so than as between the straight leg portion 103 and the greywater. To the extent that it may be desired to reduce heat transfer fromthe straight leg portion, it may be insulated. For the ranges oftemperatures, and the temperature differentials, under consideration,the undesired heat transfer in the straight leg portion may berelatively small, and it may in some embodiments be used withoutinsulation.

The outlet fresh water pipe from first pass 52 may then be carriedthrough (i.e., connected to) piping 104 to the inlet of a domestic hotwater heater 106, such that apparatus 40 functions as a pre-heater inthe hot water side of the fresh water system. The hot water pipesleaving water heater 106 feed the various hot-water taps or connectionsin the building, such as the sinks, showers, clothes washing machine,dishwasher, and so on. The grey water system may then provide the drain,or drains, for these elements, and the heat subsequently extracted fromthe grey water is used to pre-heat incoming fresh water.

As may be noted, in the embodiments of FIGS. 2 and 3, the connections ofthe transfer lines 100 of the fresh water to be pre-heated are such thatthe overall direction of travel of the water in the coiled section, beit 94 or 102, is opposite to the direction of travel of the grey waterin the corresponding cylindrical pipe, be it 64 or 78. That is, wherethe coil carries the fresh water upwards, the grey water is movingdownward. Conversely, where the coil carries the fresh water upward, thegrey water flows downward. In the embodiment shown, the heat exchangecoils of the fresh water side of the unit may penetrate the end caps atcompression fittings, indicated as 110, 112 in FIG. 4. A seal, such asan O-ring 114 may be mounted to the top end of cylindrical pipe 78 (or64). Cap 82 (or 70, as may be) seats on O-ring 114, and is held in placeby a releasable securement, such as a clamp 116. Release of clamp 116permits insertion or extraction of coil element 94 (or 102) in the axialdirection, ‘B’. In other embodiments, rather than using clamp 116, athreaded fitting may be used.

The entrance and exit of the fresh water lines to each of the heatexchange passes is above the level of the outlet drain 80 of apparatus40. That is, even when the grey water inflow is not flowing, and theunit is passive, the water level may be expected to be at the level ofthe lower lip of outlet 80. As such, the dominant portion, orsubstantially all, or all, of the coil or coils of the coiled portion 94(or 102, as may be) may tend to remain immersed even when the grey wateris not flowing. In that sense, cylindrical pipes 64 and 78 may beconsidered to be, or to define, a sump or series of sumps, or collectors122, 124, one leading to the next, in those portions lower than theoutlet overflow, e.g., that of outlet 80 or 66 as may be. That is, whereoutlet 66 is higher than outlet 80, the resting fluid level, or restingwater level, “RWL”, in sump 122 will be governed by the height of outlet66, and the resting height of fluid in sump 124 will be governed by theheight of outlet 80. Where outlet 66 is lower than outlet 80, theresting fluid level of both sumps, or sump portions, 122, 124 will begoverned by the height of the height of outlet 80.

In the alternate assembly of FIG. 3, apparatus 130 is substantially thesame as apparatus 40, except that the grey water inlet of first stage132 is at, or near, the top thereof, and the transfer to second stage134 occurs at a low level, as at transfer pipe 136 located below thecoils and just above clean-out 46. The connections of the fresh watersystem are again such as to cause the inlet fresh water in the coiledportion to flow in the opposite direction of the grey water as the freshwater advances through the turns of the coil. In this embodiment, theheight of transfer pipe 136 is well below outlet 80, so the resting greywater fluid level in both sumps is governed by the level of outlet 80.In this context, there may be considered to be two sump portions(corresponding to passes 132 and 134) of a single sump.

In the normal course of operation, fresh water is only admitted to waterheater 106 (and hence to apparatus 40 or 130) when a hot water tap isopened in the building. Customarily, that water is then drained,possibly with some time delay (after the dishes are washed, the clotheswasher fills and drains, or the bathtub or sink is emptied). The drainedgrey water, which may be warm (up to 60 C=140 F for dishwashers andclothes washers; perhaps up to 45 C=110 F for sinks, bath-tubs, andshowers) as compared to ambient indoor temperature (20-25 C=68-80 F) inthe building, is then the drainage inflow that displaces the grey waterpreviously collected in the sump of the first and second stages ofapparatus 40.

Although full counter flow embodiments are shown in FIGS. 2 and 3,alternate embodiments are shown in FIGS. 5 and 6. In contrast to theembodiments of FIGS. 2 and 3, in the embodiment of FIG. 5 theconnections of the coils are such that in apparatus 140 the axialdirection ‘A’ of flow in the helical portion of the coil as a whole (asopposed to the tangential direction flow at any point in any particularturn of the coil) is substantially the same as the direction of flow ofthe grey water in both first stage 142 and second stage 144. In FIG. 6,in apparatus 150 the direction of flow in first stage 152 is counter tothe axial direction of flow in the fresh water coil, whereas thedirection of flow in second stage 154 is in the opposite direction. Theadvantage of a system such as that of FIG. 6 is that the fresh-waterinlets and fresh outlets are consistent, which may avoid confusion oninstallation. That is, in this embodiment, the inlet is always thecenter line, and the outlet is always the radially outward line, whetherit is for the first stage of the heat exchanger or for the second stage.

In the embodiment of FIG. 7, apparatus 160 employs a double-helicalcoil, in which cap 162 has four penetrations and compression fittings,as at 164, 166, 168, 170 and two nested coils 172, 174. Coils 172, 174may be on 180 degree centers, i.e., rotated half a turn relative to eachother. Coils 172, 174 may be joined in parallel at their respective endsby tees 176, 178 on their respective inlets 180, 182 and outlets 184,186. The designation “inlet” and “outlet” is arbitrary, and depends onthe direction of the flows as the apparatus is installed. The provisionof doubled coils may tend to increase the heat transfer surface areabetween the fresh water flow and the grey water flow, may also tend toincrease the time (on average, double) that the fresh water fluid takesto traverse the heat exchanger stages; and, to the extent that multipleflow channels may have a greater total cross-sectional area than asingle flow channel, may also tend to reduce the flow resistance in theheat exchanger. Doubled coils may be used in any of the foregoingembodiments. It is also possible to have more than two coils—there maybe three or four. Although it is assumed that each coil member iscircular in cross-section, they need not be. They could, for example, beoval or rectangular. It is not necessary that the coils have the samediameter or cross-sectional area as the inlet or outlet pipes—severalparallel coils each of smaller diameter may in total have the same orgreater cross-sectional area as the single inlet and outlet fresh waterpipes. Whether one, two, or more, coils may be mounted in each heatexchanger stage, the adjacent coil turns may be held in spaced apartrelationship in the axial direction of the outer cylindrical pipe (be it64 or 78) by retainers, or spacers, or spiders, (not shown).

In the embodiments shown, the pressurized fresh water lines do notrequire radial penetrations of the cylinder side wall. Rather, thejunction is in the end closure fitting or end plug, or cap, or closure,or closure member. A plug could also be installed in a side wall of theunit. The use of a standard fitting or cap, or plug, permits a knownmating between the plug and the seat of the cylinder, which is a knownmating technology, of wide availability, and of understood simplicityand reliability. It is a known technology, that is used also at thesolid end or closure or plug that caps off the bottom end of thecylinder as well. In the embodiments of FIGS. 2, 3, 5 and 6, the bottomclosure of each pass is governed by one or another of the clean outfittings, be it a drain fitting, or trap, or valve, 76. In operation,with the clean out fitting closed, the bottom closure may be consideredas functionally equivalent to a blind end fitting or cap, or plug, i.e.,without any fresh water line penetrations, as if it were a solid blankor cap through which flow does not occur. Flow only occurs through thatend when the system is being flushed, e.g., to clean out debris. Whereapparatus 40 is monitored or controlled by an electronic controller ortimed or programmed device, the flushing or clean-out step may occurperiodically, such as once a day, once a week, or once a month, and mayoccur at a time when it is not likely to affect operation, e.g., in themiddle of the night. Given that cylinder 64 accommodates the heatexchange coil, cylinder 64 may be larger in diameter than the inlet,outlet, flushing, overflow, and other grey water flow pipes described.The coil can be pre-formed, mated with the pipe stems, and the pipe stemfittings mated to, or potted in, the end closure fitting or cap or plug.Installation (and removal or replacement, as may be) occurs by axialtranslation of the coil in the cylinder. In one embodiment the pipe maybe ABS pipe. The pipe may be of nominal 5″ dia, with a 5″ insidediameter in which a helical coil (or coils) of 4″ or 4½″ outsidediameter of coil copper pipe may be located. In another embodiment thepipe may be 6″ nominal diameter, with a 6″ inside diameter wall housinga 5″ or 5½″ diameter helical coil (or coils) may be installed. In eachcase, the first pass (or second pass, or third pass, etc.,), andtherefore the respective reservoir, or receptacle, sump or sump portion,has a shell wall defined by the pipe. Each of those cylinders, or passesor receptacles or sumps may tend to be elongate—that is, substantiallylonger in the axial direction than wide in terms of diameter. In generaluse these members may be upstanding, being upright or predominantlyupright. In a tall thin reservoir or sump, the depth and volume of thesump tend to be large as compared to the surface area of the liquid inthe sump. In one example, the hydraulic diameter of the resting liquidsurface may be less than one tenth of the depth of the sump below theoutlet.

The penetration of the closure fitting can be potted in an epoxy orother moulded compound to form a durable seal. As the fittingpenetration is located above the level of the drain, and therefore abovethe resting fluid level in the sump, even if the fitting should beimperfect, or if it should loosen over time, it may tend not to resultin leakage, and it may tend even then to be relatively easy to obtainaccess to the fitting for repair or replacement.

Further, in the embodiments shown, the cylinders may tend to besubstantially longer than their diameter, such that the axial flowlength is much longer than the diameter of the cylindrical pipe, e.g.,10 times the length, or more. In one installation, the overall height ofthe cylinder is between 4 ft and 7 ft, with a diameter of about 4inches. That is, the height may be intended to fit within the clearanceprovided by an 8 ft ceiling, and may be approximately the same as, orcomparable to, the height of a water heater, which may typically beabout 5 ft, the size depending on whether the tank is nominally 30, 40,50, or 60 gallons. It may be that the overall height of the heatexchanger apparatus may be in the range of 2/3 to 3/2 of the height ofthe adjacent water heater 106. Two adjacent cylinders may be held on acommon base, 118, and may be spaced from each other by yokes or framemembers 120. There may be three or four such cylinders held together ina bundle. Although such a bundle of pipes might be arranged with thelong axis of the pipes oriented horizontally, and the outlet at a heightto maintain a resting fluid level of grey water in the cylinders assumps, it may be more convenient, and more compact in terms of floorspace occupied, for the cylinder bundle to be arranged vertically, orsubstantially or predominantly vertically, or upright. The pre-heaterheat exchange or heat recovery apparatus, 40, may be mounted beside thehot water heater, in a furnace or other utility room, for example, andmay occupy a physical footprint of comparable size, or less.

FIG. 8 shows a possible bundle arrangement in which the first and secondpass cylinders 64 and 78 are placed tightly proximate to each other on acommon base 118 (shown, in this instances, as being a round circularbase, or plate 126) with inlet and outlet (or upper and lower) elbows66, 67 angled on a V (when seen from above, the V being defined by theintersection of the lines of centers drawn, respectively, between thecenter of pipe 64 and the center of pipe 72; and between the center ofpipe 78 and the center of pipe 72) such that transfer pipe 72 is nestedclose into the space between the two cylindrical pipes. As shown, pipe72 may then lie within the smallest circle that circumscribescylindrical pipes 64 and 78. In some embodiments, if a tangent line isdrawn across the top edge of cylinders 64 and 78 closest to pipe 72, theproximate edge of transfer pipe 72 traverses that tangent such that theproximate edge is closer to the line of centers of pipes 64 and 78 thanis the tangent line. There may be end closure plates 126 at top andbottom, and the entire assembly may be enclosed within a cylindricalshell or closure member, or skin, or housing, or cowling 128 that runsbetween the top and bottom members. The inlet pipe 58 and outlet pipe 80may be mounted on the same side and parallel, as shown, for easy accessand installation, or may be mounted on opposite sides, or on 90°spacing.

FIG. 9 shows an alternate embodiment to that of FIG. 8, in which theheat exchanger arrangement or assembly 190 has more than two stages inseries, as indicated by first second and third stages 192, 194 and 196.The stages are arranged in a generally counter-flow arrangement to theflow of waste water. These stages are substantially similar to thoseshown in FIG. 8, but there are three rather than two, mounted on acommon base 198. All of the cylindrical members and transfer tubes ofassembly 190 fall within the projected plan profile of base 198 as asingle, tight bundle. Assembly 190 illustrates that the cylinders in thebundle need not have axes all lying in the same plane. In assembly 190,while the axes are mutually parallel and defining the vertices of atriangle, such that the pipes are mounted side-by-side in a triangularconfiguration. Base 198 may have the form of a round plate by which theother items are circumscribed. A more-than-two-stage heat exchanger maybe used where, for example, the vertical clearance is more limited. Itmay be that rather than having an 8 ft or 9 ft ceiling, where a 6 ft or7 ft tall heat exchanger assembly might be used, there may be only 48,60 or 72 inches of vertical clearance. For the same length of heatexchange coil surface, three shorter coils may be used instead of twolonger coils. Similarly, four passes could also be used. As in FIG. 8,there may be top and bottom plates or end closures, and an enclosingperipheral wall, or shell, or cowling, by which the assembly isenclosed. Again the inlet pipe 58 and outlet pipe 80 may be on the sameside and have parallel center line axes, or may be mounted on oppositesides, or on 90° spacing.

In the embodiments shown, as for example in FIGS. 8 and 9, a compactarrangement may facilitate mounting of the heat exchanger assembly in abasement, or utility room, and may in some instances permit the heatexchanger assembly to be mounted to a main drain stack, such as atypical 3″ diameter stack pipe, rather than necessarily beingfloor-mounted.

In the embodiment of FIGS. 10a and 10b , a heat exchanger arrangement200 is substantially similar to that of FIG. 2. However, as illustratedit has a pair of coils 202, 204 in each heat exchanger pass 206, 208respectively. In this example the coils may be ½″ copper or stainlesssteel pipe, that have been teed off a ¾″ supply line. The coils arewound on a common diameter and are nested axially, such that the turnsof the coils alternate along the combined coil. Similarly, the returnlegs 210, 212 may run side-by-side back to the top of the unit, wherethey may again be teed back together, or fed to the adjacent pass as atwin line. For ease of modularity and facilitation of assembly andinstallation, a single entrance fitting and a single exit fitting (asopposed to a dual fitting) may be convenient. In one embodiment thecoils may be teed together at the bottom end of the leg, and only asingle, larger diameter, return leg may penetrate the top closure cover.

In FIG. 10b , the front sides of the coils have been removed to revealan inner pipe 214 of smaller diameter. Pipe 214 is nested within outerpipe 78, such that coils 202, 204 locate in an annular cavity 216between pipe 214 and pipe 78. For example, pipe 78 may be a 6″ i/d pipe,and pipe 214 may be a 2″ i.d. pipe, such that the annulus is 2″ wide,less the thickness of the 2″ i.d. pipe wall (the thickness of a Schedule40 pipe being typically 3/16″, such that the outside diameter is about2⅜″). Pipe 214 is blocked to prevent wastewater flow therethrough. Itmay be blocked by being mounted to, or capped by, end cap 218, or it maybe blocked by an internal wall or baffle, or by a bottom end cap locatedat the entrance of the return legs, or leg. It may be relativelyconvenient for pipe 214 to be blocked by the attachment to end cover, orclosure, or cap 218. Alternatively, or additionally, pipe 214 may beblocked by thermal insulation 228. That is, after installation of thereturn leg or legs 210, 212, the remaining space within pipe 214 may befilled with insulation, such as an expanding foam insulation. Such foam,when cured, may tend to block flow of waste water, may tend to insulatethe return leg or legs, and may tend to stabilise the position of thereturn leg, or legs, within pipe 214.

The use of an internal filler element to occupy a greater portion of thespace inside the coil may also be used in any of the embodimentsdescribed above, whether they employ single tube coils, double tubecoils, or coil assemblies of more than two pipes. As in the embodimentof FIGS. 10a and 10 b, the central tube is obstructed to prevent flow ofthe other fluid, i.e., the waste water, and the blockage may be obtainedby capping the tube, by virtue of its dead-end attachment to the cap, orby the use of a flow impeding filler material such as an insulatingfoam. Although pipe 214 is conveniently mounted concentrically with thecoil, and the return legs are mounted substantially centrally orsymmetrically within pipe 214, that need not necessarily be. Pipe 214could be eccentrically mounted, and it is not necessary that the returnlegs be mounted within pipe 214. The return leg or legs could runparallel to pipe 214, or could be sound about it, e.g., in an helicalmanner. It may, however, be convenient, and may facilitate manufacturefor pipe 214 to be concentric with the coil, and, as installed, with theouter casing of the pass. The filler element, namely pipe 214, is shownas having a diameter that is about, or somewhat more than ⅓ of theinside diameter of the outer shell casing (i.e., nominal 2″ i.d. pipe(really 2⅜″ o.d.) over a nominal 6″ i.d.). The filler could be of adifferent size. It could be as little as ⅕ the diameter, and as much as½ or ⅔ of the inside diameter of the outer pipe.

In this context, when the term “diameter” is used, the issue is thehydraulic diameter of the resulting flow passageway, defined byD_(h)=4A/P, where A is the area of the passageway and P is theperimeter. Reducing the hydraulic diameter, D_(h), may tend to increasethe effectiveness of heat transfer. Here, in one embodiment the annulusthickness is about 2″, or a bit less (1 13/16″), and the outsidediameter of the nominal ¾″ copper coils may be ⅞″, such that the coiloutside diameter is approximately half of the passage width (i.e.,(⅞″)/(1 13/16″)= 14/29=approximately half). The ratio could be between ⅓and ⅔; or perhaps between ⅖ and ⅗. However ½ is convenient. While FIGS.10a and 10b illustrate a two pass arrangement, the arrangement couldhave a different number of passes, be it three, or four, or some othernumber.

In one embodiment, the apparatus included heat exchanger modulesemploying stainless steel coils in a 6″ i.d. pipe, with a central 2″i.d., Schedule 40 pipe mounted to cause waste water flow in the annulus.The apparatus was run with an inlet flow equal to the outlet flow at 10L/min (approx. 2½ US Gal/min). In a two pass arrangement in series, witha fresh water inlet temperature of 16.2 C, and a waste water inlet at 40C, The fresh water temperatures were 16.2 C at inlet to the first stage;20.4 C at the mid-point between stages; and 27.1 C at the outlet leadingto the water heater. The waste water temperatures were 40 C at inlet;33.3 C at the mid-point; and 27.2 C at the outlet. The mean drop acrosseach coil from hot side to cold side was 13 C, and, for a hot waterheater outlet temperature of 55 C (130 F), the heat recovery was 28% ofthe heat input otherwise required to heat the water to the desired 55 Coutput temperature. Taking a measure of efficiency of(27.1-16.2)/(40-16.2=10.9/23.8=46% of potential heat recovery. Using thesame modules in three units in series, at the same flow rate, thecorresponding temperatures were fresh water inlet 17.2 C; firstmid-stage temperature 20.1 C; second mid-stage temperature 24.7 C;outlet 30.1 C to hot water heater inlet. Waste water inlet 40.2 C;second mid-stage 35.7 C; first mid-stage 29.6 C and outlet 26.6 C. Themean drop across the coils from hot side to cold side was 9.5 C. For thedesired 55 C water heater outlet temperature, the pre-heating wasproviding 34% of the heating load that would otherwise have to beprovided by the heater. The corresponding measure of overall heatexchanger efficiency was (12.9/23.0)=56% of the potential recoverableheat. These measurements were taken in summer, when the inlet freshwater temperature is relatively high (17 C). In the winter, the inletwater temperature may be as low as 4 C. A larger temperature droppotential may tend to increase the potential heat recovery, and also toincrease the relative efficiency. It may be noted that in the example,the coils are free of additional fin-work and free of the soldering,brazing, or other manufacturing steps associated with making morecomplicated fin-coil or finned-tube heat exchangers.

In FIGS. 11a -11 d, there is an embodiment of heat exchanger apparatusindicated generally as 220. The external casing and piping may be takenas being substantially the same as those of the embodiments previouslydescribed. They may vary in aspect ratio. For example, the externalcasings of first, second, and third passes 222, 224, and 226 may be 6″or 8″ diameter pipes. First, second, and third passes 222, 224 and 226may be understood to be assembled and connected in a series, orcounter-flow, configuration relative to the waste water flow path. Eachof the passes may be taken as being of substantially the sameconstruction, unless indicated otherwise. Apparatus 220 may differ fromthe apparatus previously described in having a set of longitudinal tubes230 running between an inlet header at top end cap 240, or manifold 232,and a return or collector, or outlet manifold or header 234 at the farend of the assembly distant from top end cap 240. Inlet manifold 232 isconnected to a first, or inlet, pipe 236. The outlet manifold isconnected to a second, or return, pipe, or leg, 238. It may beconvenient for the return leg to be centrally mounted to header 234, andto pass centrally through header 232 without being in fluidcommunication therewith. Inlet header 232 may have the form of an hollowcylindrical disc, or plenum that feeds tubes 230. Outlet header 234 maybe similar. In one embodiment, the end cap of return header 234 may havea domed shape. It may also be convenient for the members of the set orarray of tubes 230 to be mounted in an array that is concentric withreturn leg 238, although this need not be so. It is not necessary thatreturn leg 238 be straight. It could be curved. It could be helical.Similarly, tubes 230 need not be straight. They could be angled orcurved or helical. It is convenient that they be straight and parallel.As may be understood from FIG. 11c , tubes 230 may include an inner setof pipes 242 and an outer set of pipes 244, which may be arrangedconcentrically, as indicated. As also indicated, the end of returnheader 234 may be rounded or bulbous.

Tubes 230, manifolds 232, 234, inlet pipe 236 and outlet pipe 238 maycombine to form a single tube bundle assembly 250. Assembly 250 may thenbe installed or removed as a single pre-assembled unit. To that end,manifold 232 has a peripheral flange 246 suited for attachment bythreaded fasteners to the end of the outer housing shell pipe wall. Tothat end the outer housing shell pipe wall may have a correspondingthickened end or ring or flange, which may itself have correspondingtapped bores. As may be noted, outlet pipe 238 passes through both theinner and outer walls of inlet manifold 232. Seals are made on bothwalls with compression fittings 248. Outlet pipe 238 may be encased ininsulation as at 228, or in a jacket that serves to reduce the flow pathcross-sectional area in the remainder of the chamber inside the outerjacket. As with the other embodiments, whether a pipe is an “inlet” oran “outlet” is at least to some degree arbitrary. In general, thearrangements of inlets and outlets may typically be intended to causethe flow of heating and cooling fluids to be in opposite directions. Aswith the other embodiments, assembly 220 may include two heat exchangerpasses, or three, as shown, or four, or some other larger number as maybe.

In the embodiments shown, other than the forming of the coilsthemselves, the assembly may be made with readily available, standardfittings of copper pipe (or stainless steel pipe) and plasticcomponents. It is intended not to require rare or specialised moldedparts. That is, even if repair or replacement of parts is required manyyears after original installation in a relatively remote location, thereis a fair possibility of obtaining standard replacement parts at ageneral hardware or building supply retail outlet. It may not requirethe shipment of a unique original equipment manufacturer part that maybe of limited availability or high expense, or both.

In the embodiment of FIGS. 12a-12d , a heat recovery apparatus 260 mayhave a grey water supply fed into a first member, or conduit, orpassage, or piping, or chamber 262 such as may have the form of acylinder 264, which may be a cylindrical canister with an inlet at oneend, as at inlet 266 at the top; and an outlet at the other end, as at268 at the bottom. As with the other embodiments, the terms “inlet” and“outlet” are somewhat arbitrary, depending on how the fluids are runthrough apparatus 260. A second member, or conduit, or passageway, orchamber, or tubing or pipe, etc., defining a chamber, 270 may be mountedabout chamber 262. Second member 270 may be an annular canister or tube272 mounted about first member 262. So that a thermally conductive pathmay be obtained, second member 270 may be shrink fit on first member262. Alternatively, thermally conductive members may be sandwichedbetween the outside surface of 262 and the inside surface of 270. It maybe convenient that the two members be concentric. Member 270 has a freshwater outlet as at 274 and an inlet as at 276. Inlet 276 may bebifurcated (or may have several inlet legs or return legs, however theymay be called depending on the direction of flow), as at 278, that meetin, or extend away from, a common manifold, as at 280. Either or both ofoutlet 274 and inlet 276 may have multiple branches connected by acommon manifold. A third member 282 such as may be a conduit, pipe,tube, chamber, etc., may be indicated as an annular outer cylinder orcanister 284. As before, it may be mounted concentrically about members262 and 270, and in one embodiment it may be shrink fit onto the outsideof member 270. Third member 282 may have an inlet, or inlets, 286 thatis, or are, fed from outlet 268 of first member 262. The lowermost pointof the connecting piping may also have a sump drain, such as may becontrolled by an outlet valve 290, which may be a solenoid controlledvalve. Third member 282 has an outlet 288, which may be taken as beingthe same as outlet 80, above. Optionally, either or both of members 270and 282 may have vanes or a helical baffle or baffles, indicatedrespectively at 292 in member 270 and at 294 in member 282, such as maytend to cause the flow to move in a swirling or helical path and such asmay tend to enhance heat transfer to the respective conductive walls.Alternatively, either or both of the grey water or fresh water inlets tomembers 270 and 282, respectively, may be arranged tangentially in sucha manner as to impart a circumferential component of velocity to theflow inside the various canisters. Alternatively, flow directingmembers, or baffles, may be mounted in a maze, or zig-zag, or serpentinearrangement such as may tend to enhance heat transfer at the conductionwall.

In this embodiment, either of the outside wall of member 270 or theinside wall surface of member 282 may have splines or flutes 296. Thesame may also apply at the interface between item 262 and item 270. Thedouble-walled interface between member 262 and member 270; and betweenmember 270 and member 282 may tend to require a double failure for theflow of fresh water and waste water to mix. Inasmuch as the bottom ofthe unit is open, in the event of even a single failure, dripping fromthe bottom of the unit may tend to indicate that a failure has occurred.The unit may be provided with an electronic moisture sensor to triggeran alarm condition in the event of moisture detection in the bottom ofthe unit. Where there is grooving at the interface between the units, asdue to splines or flutes, such grooving may tend to permit any leavingmaterial to drain.

Assembly 260 may be connected, e.g., in series, with other suchassemblies as in the manner of the other modules described above.However many such modules there may be, they may be enclosed within ahousing, such as cowling 128. Such an enclosure may have a leak drain,internal moisture sensor, and alarm, as discussed.

As noted in respect of the other embodiments described above, it may bearbitrary which is an “inlet” and which is an “outlet”. Likewise, thesense of fresh water inlet and outlet could be reversed such as to causethe inlet flow to be generally in the opposite direction to the flow inthe outer grey water canister.

In the embodiment of FIG. 13, rather than having a three-layeredconcentric unit of members 262, 270 and 282, a heat exchanger assembly300 may have a single fresh water member or canister 302 nestedconcentrically within an outer waste water canister 304. As before,there is a double-walled interface between the fresh-water and wastewater sides of the unit.

The drawings of the Figures may not be to scale. As noted above, in FIG.12a , the outside diameter of member 262 may be 2 inches, correspondingto the inside diameter of member 270. The outside diameter of member 270may be 3 inches or four inches, which corresponds to the inside diameterof member 282. The outside diameter of member 282 may be 4 inches (wherei.d. is 3 inches) or 5 or 6 inches (where i.d. is 4 inches). In terms ofgeneral proportions, the overall height of the canisters, indicated ash₂₆₀, in respect of assembly 260 of FIGS. 12a-12e , and h₃₀₀ in respectof assembly 300 of FIG. 13, may be of the order of 1 m or 40 inches. Itcould of course be as short as 30″ to 36″, and as tall as 60″, 72″, or78″. In one particular embodiment, the inner canister may be about 2″ (5cm) in diameter, the fresh-water annulus may have a radial thickness ofabout ½″ (13 mm) (giving an outside diameter of about 3″ (7½ cm)). Theaspect ratio height to diameter of the unit, assembly 260, overall, isthen about 10:1. The aspect ratio may be in the range of about 5:1 toabout 20:1. For assembly 300, the overall aspect ratio ranges may beroughly the same. The various tubes and canisters may be made of metal,such as copper or stainless steel, and the parts may be assembled as byheat shrinkage onto each other. The connection at the grey water inletmay include an adapter between a non-metallic pipe, such as ABS, and ametallic pipe of the heat exchanger assembly, be that pipe copper orstainless steel, for example. The connections to fresh water supply andto the water heater, and the connections to the grey water drains andstack may be understood as being the same, or substantially the same, asdescribed above. The fresh water supply conduit may typically be takenas ¾ inch copper upstream and downstream of the unit, be it 260 or 300.

A further embodiment of a grey water heat recovery apparatus 320 isshown in FIGS. 14a and 14b . It may be taken as being the same as theapparatus of corresponding FIGS. 11a -11 d, with like parts beinglabelled with the same annotation numerals. FIG. 14a shows a single pass322 of apparatus 320, and may be understood as being genericallycomparable to any of the passes shown in FIG. 11a with correspondingpipe connections as may be. Apparatus 320 is shown with an externallayer of thermal insulation, or a thermal insulation jacket, as at 324.In the embodiment shown, jacket 324 extends from the top of the outerwall to the bottom of the outer wall close to valve 76. Further thermalinsulation mounted to extend around the inlet and outlet waste waterconduits, as at 326 and 328. The outside wall structure of the greywater sump, that is, of shell 78, may be made of stainless steel or ABSplastic.

Apparatus 320 includes a heat exchanger fresh water pass or core orbundle or tube bundle assembly 330 that has the same structure as tubebundle assembly 250, having a set of longitudinal tubes 230 runningbetween an inlet header at top end cap 240, or manifold 232, and areturn or collector, or outlet manifold or header 234 at the far end ofthe assembly distant from top end cap 240. Inlet manifold 232 isconnected to a first, or inlet, pipe 236. The outlet manifold isconnected to a second, or return, pipe, or leg, 238. It may beconvenient for the return leg to be centrally mounted to header 234, andto pass centrally through header 232 without being in fluidcommunication therewith. Inlet header 232 may have the form of an hollowcylindrical disc, or plenum that feeds tubes 230. Outlet header 234 maybe similar. In one embodiment, the end cap of return header 234 may havea domed shape, all as described above in the context of FIGS. 11a -11 d.As above, it may also be convenient for the members of the set or arrayof tubes 230 to be mounted in an array that is concentric with returnleg 238, although this need not be so. It is not necessary that returnleg 238 be straight. It could be curved. It could be helical. Similarly,tubes 230 need not be straight. They could be angled or curved orhelical. It is convenient that they be straight and parallel. As withthe other embodiments, whether a pipe is an “inlet” or an “outlet” is atleast to some degree arbitrary. In general, the arrangements of inletsand outlets may typically be intended to cause the flow of heating andcooling fluids to be in opposite directions. As with the otherembodiments, assembly 320 may include two heat exchanger passes, orthree, as shown, or four, or some other larger number as may be.

Assembly 330 may then be installed or removed as a single pre-assembledunit. Tube bundle assembly 330 differs from assembly 250, however, inthat it is internally coated, or externally coated, or both internallyand externally coated, in a non-electrically conductive coating, asindicated notionally at 332. It is applied to all surfaces, such that acontinuous electrical barrier is formed. Coating 332 may be of small orvery small thickness relative to the size of the parts of apparatus 320generally. In one embodiment the non-electrically conductive coating maybe paint, or enamel, or epoxy. A non-conductive or dielectric coatingmay be a hygienic polyurethane or silicone compound. The non-conductivecoating may be applied, either internally or externally, e.g., as bydipping in a bath, followed by subsequent curing. However applied, thenon-electrically conductive coating is, and functions as, anon-conductive coating between the fresh water and waste water paths ofthe heat exchangers.

Assembly 330 is also provided with one sensor or one terminal (which maybe an array of sensors or terminal ends distributed to various locationsalong the fresh water flow path) indicated as 334 of an electricalconductivity sensor assembly or circuit, 340. In some embodiments, thefirst sensor may be located in one of the end manifolds of the tubebundle, and, in particular, it may be located in the upper manifold. Asecond terminal, or an array of second termini, 336 is similarly locatedin the waste water pass. Terminal 336 may be located below the standingwater level of the sump, i.e., below the resting water level RWL of theparticular sump. In some embodiments it may be located near the bottomof the sump, and the wiring of the sensor may be run back to the top ofthe sump, and pass through the shell wall where it may be twinned withthe lead of the other sensor terminal and joined in a common plug orconnector. Electrical conductivity terminals 336 may be mounted in eachsump of each pass of the waste water heat recovery apparatus to permitdetection of a leak in whichever pass it should occur. Terminals 334 maybe mounted in each fresh-water pass, and may be formed into a combinedterminal connector for each pass, as at 354. In another embodiment, asingle terminal 334 in a continuous fresh water path may also be used,since a rise in conductivity in any of the sumps will be sensed in thefresh water line.

Electrical conductivity sensor assembly or circuit 340 may be acapacitance based or a resistance based conductivity sensor assembly.That is and said leak detection circuit senses at least one of (a)resistance; and (b) voltage potential between said fresh water flow pathand said grey water flow path. It may include a power supply 338. Powersupply 338 may be a DC supply of low or very low voltage. This powersupply has a power storage capability, e.g., such as a battery, suchthat it will continue to operate if electrical power has failed in thebuilding more generally, as in the case of a power outage. That is, leakdetection circuit 340 includes a storage member, e.g., a battery, whichoperates to provide power independently of the availability of externalpower such as from municipal power or from building power generally.Thus, even if fresh water pressure is lost due to an electrical pumpfailure or other upstream flow interruption or shut off, for example,circuit 340 will remain in operation. Circuit 340 may also include asignal output annunciator or alarm or display, indicated at 342, whichmay include a normal signal (e.g., a green light) to indicate that thesystem is in operation but not in a fault condition; and an alarm signalwhether noise-making or visual, or both, or that sends an electronicmessage to a message receiving device, such as a phone or e-mailaddress, or any combination of them (e.g., a red light, or fault, oralarm condition). Display 342 may be part of a controllingmicroprocessor, or controller 344. In normal operation, circuit 340detects an open circuit between terminal 334 and terminal 336. However,in the event that a leak should develop between the fresh water systemand the waste water system, circuit 340 detects a conductivity path, andprovides an alarm signal corresponding to that red light, fault, oralarm condition.

Electrical conductivity sensor circuit 340 may also control theoperation of valves by which to adjust operation of assembly 330 from afirst condition or position or configuration (e.g., normal operation) toa second condition or position or configuration (e.g., a fail-safecondition). That is, assembly 330 may be provided with a first solenoidcontrolled valve (S1) indicated as 346 and a second solenoid controlledvalve (S2), indicated as 348. It is arbitrary which valve is designatedas the first or second valve.

Considering the elements as also shown in FIG. 1, the detection ofelectrical conductivity between terminals 334 and 336 is interpreted asbeing an indication of a leak between the fresh water and waste watersides of the heat exchanger. In normal operation, this should be benign,since the fresh water system is pressurized typically at 30-50 psi., andthe waste water system is essentially at ambient, i.e., less than 5psi., such that any leak will flow away from the fresh system to thewaste system, and not into the domestic supply. However, in the eventthat source pressure is shut off in the fresh water system, and a leakis detected, the first of the solenoid controlled valves, 346 opens thesump drainage valves and dumps the waste water sumps (however many theremay be) directly to drain 30. At the same time, the second of thesolenoid controlled valves 348 opens the fresh water bypass 350, suchthat fresh water supply is directed around the waste water heat recoveryapparatus and directly to water heater 106 (or to such other fresh watersupply line as may be, whether hot or cold). Where source pressure isapplied through the bypass valve 348, a check valve is positioned in thefresh water output line 104 is placed to prevent back flow into thewaste water heat recovery heat exchanger passes. Apparatus 320 may alsobe provided with a fresh water shut-off valve 352 which may beco-operably mounted with fresh water bypass valve 348, and that mayprevent additional fresh water from flowing into the waste water heatrecovery apparatus. In some embodiments, the respective sump valves 76may be the solenoid controlled valve, or valves, 346.

The leak detection features of apparatus 320 may be applied to the otherembodiments shown or described herein, whether having coils or tubebundles. The leak detection circuit operates to govern whether flow isdirected (in one mode) through the fresh water flow path or (in anothermode) through the fresh water bypass e.g., directly to the water heater,as when a leak is detected. Similarly, the leak detection circuitgoverns whether grey water is directed in a first mode to the grey waterflow path, or, in a second mode, is directed to the drain.

In the embodiments shown, other than the forming of the coils or tubemanifolds themselves, the assembly may be made with readily available,standard fittings of copper pipe, or mild steel pipe, or stainless steelpipe, and plastic components. Other than the tube manifolds, it isintended not to require rare or specialised molded parts. That is, evenif repair or replacement of parts is required many years after originalinstallation in a relatively remote location, there is a fairpossibility of obtaining standard replacement parts at a generalhardware or building supply retail outlet. It may not require shipmentof a unique original equipment manufacturer part that may be of limitedavailability or high expense, or both.

FIGS. 15a-15g illustrate an alternate form of tube bundle assembly 360to that of item 230 of FIG. 11a or 250 of FIG. 11d . It has an uppermanifold 356, a lower manifold 358, a first member identified as centralpipe or central tube 362, and a second member, or second members in theform of a surrounding array of pipes or tubes 364 that extend betweenthe upper and lower manifolds 356, 358. As before, tube 362 and array oftubes 364 carry fresh water under pressure. Also as before, whicheverdirection the fresh water may flow in central tube 362, it flows in theopposite direction in tubes 364. In that context, whatever direction thewater may flow, tube or pipe 362 may be referred to as the “return”.This choice is arbitrary, and, as above, depends on the fresh water pipefitting connections. The “return” passes through the upper manifoldwithout being in fluid communication with the upper manifold. The returnthen extends upwardly beyond the upper manifold to define one or theother of inlet or outlet pipes 92 and 98. As illustrated, it isarbitrarily designated as fresh water outlet pipe 98. Accordingly, asabove, both the inlet and outlet fresh water pipes 92, 98 have theirends located for connection at one end of tube bundle assembly 360,namely at the top end, above the resting water level in the sump.

As before, upper manifold 356 is bounded by upper and lower closureplates, or bulkheads, identified as upper and lower annular plates 366,368; and by inner and outer peripheral walls, namely inner wall 370 andouter cylindrical wall of larger radius 372. Although these peripheralwalls need not be circular cylinders, it is convenient that they are.The outer radius of lower annular plate 368 and the outer radius ofouter cylindrical wall 372 are such that their diameters seat closelywithin, and may seat in a gentle interference fit within, the insidesurface of the outer cylindrical wall defined by a cylindrical pipe 64or 78, such as previously seen in FIGS. 2, 3, 5, 6, 10 a and 11 b, forexample. As before, that cylindrical pipe may be plastic. Alternatively,it may be metal (e.g., copper, mild steel, or stainless steel), and maybe wrapped in an external layer of thermal insulation. The outerdiameter of upper plate 366 may extend, and in the illustratedembodiment does extend, radially outwardly proud of cylindrical wall372, such as to define a peripheral flange 374. The annular surface offlange 374 may seat on the end of pipe 64 or 78, and may be securedthere with fastening hardware, such as bolts passing through the holesseen at 376. Alternatively, as illustrated in FIGS. 15c and 15d , pipe64 or 78, as may be, may include a straight cylindrical pipe portion,and, additionally, at one end, namely the upper end as illustrated, theassembly may include a pipe coupling 68 mounted to the outside of thepipe. In the embodiment illustrated, the depth of inlet or uppermanifold 356 is less than the axial length of pipe coupling 68, suchthat when part of pipe coupling 68, i.e., its lower margin, is mountedto the pipe, the remainder of coupling 68 leave an internal cavity oraccommodation of the diameter of the inside of the coupling, axiallyabove the shoulder defined by the end of the cut pipe. As such, uppermanifold 356 seats within this larger diameter cavity, since the outsidediameter of the outer peripheral wall 372 is the same, or substantiallythe same, as the outer diameter of the cut pipe. A circular seal, orO-ring may also be provided for location between flange 374 and the endof the respective pipe coupling 68, as may be. The inner diameter ofannular cylindrical wall 370 provides a clearance passage for returnpipe 362. An annular bushing or seal 378 may be located in this space tocenter pipe 362 relative to wall 370, and therefore relative to uppermanifold 358 generally. In the examples given, members 64, 78 and so onmay be 4″ nominal diameter ABS pipe, and coupling 68 may be acorresponding 4″ standard pipe coupling. Cylindrical wall 372 and flange374 may be sized accordingly. Other standard sizes of diameter pipe andstandard pipe couplings could be used, e.g., 5″ or 6″, whether ofplastic, steel, or stainless steel, as may be. As noted, the use ofstandard, commercially available pipe sizes is intended to simplifyconstruction and repair or maintenance such as may be required. The useof coupling 68 may facilitate assembly and increase the room availablefor the inlet and outlet ports for the fresh water. For example, whereoutlet pipe 98 is on the axial centerline of the unit, the use of pipecoupling 68 permits inlet pipe 92 (of the same standard dimension asoutlet pipe 98) to be mounted in top wall 366 as well, within the roomprovided by the diameter of outer peripheral wall 372.

As before, plates 366, 368 and cylindrical walls 370, 372 co-operate todefine an enclosed volume or chamber 380 that has a port connected tofresh water inlet pipe 92, and outlets connected to each of the pipes364 of the array of tube bundle assembly 360. It may be noted that freshwater inlet pipe 92 may be the outlet pipe, depending on the manner ofconnection. Pipes 92 and 98 (or 362) may be, and in the embodimentillustrated are, of larger diameter than the pipes of the heat exchangerarray, namely pipes 364. Pipes 92 and 98 may be, and in the embodimentillustrated are, of the same diameter, and may be ¾″ (20 mm) pipes suchas are commonly used in residential water supply systems in NorthAmerica. Pipes 364 may be, and in the embodiments illustrated are,smaller in diameter, and may be, for example, ¼″, ⅜″ or ½″ pipes. Thetotal cross-sectional area of pipes 364, summed together, may be, and inthe embodiment illustrated is, as great as, or greater than, thecross-section of either of pipes 362 (or 98) and 92. The array of pipes364 may meet the ports, or holes, or fittings of lower plate 368 on apitch circle, D₃₆₄ which is twice the pitch circle radius, R₃₆₄indicated in FIG. 15e . The pipes of that array may be equally spacedaround the pitch circle. This apparatus also has an air bleed valve at382.

Looking at the lower end of heat exchanger tube bundle assembly 360,lower manifold 358 has an upper plate 384, a lower plate 386 and anouter peripheral wall 388 that co-operate to form an enclosed space orchamber 390 that is contained within the end cap or dome defined bylower plate 386 as before. Upper plate 384 has ports, or opening, orholes, or accommodations, or seats, or fittings formed in it to receivethe lower ends of return pipe 362 and of pipes 364. As may be seen inFIG. 15f , the opening 392 for pipe 362 may be, and in the embodimentillustrated is, located centrally in plate 384. Respective openings 394for pipes 364 may be, and in the embodiment illustrated are, equallyspaced around a pitch circle having a diameter D₃₉₄, which is twice theradius R₃₉₄ indicated in FIG. 15 f.

Plate 384 has an outer peripheral diameter indicated as D₃₈₄. It alsohas protrusions, or tabs, or tangs, or abutments, or spacers, or toes,or fingers, or ears, indicated as 396, however they may be called, thatextend or protrude radially outwardly proud of, i.e., radially beyond,the outer peripheral diameter D₃₈₄. Fingers 396 define a spider thatcenters the lower end of tube bundle assembly 360 within pipe 64 or 78,as may be. In some embodiments fingers 396 may be dimensioned to fitclosely within the inside wall of pipe 64 or 78, and may touch thatwall. Three such fingers are sufficient for centering, although agreater number may be used. In the embodiment shown there are four ears396. They are spaced equally around plate 384. In any event, spaces, oraccommodations, or gaps, or reliefs, or rebates, or openings, orpassageways 400 are formed about the periphery of plate 384, in the opensectors remaining in the generally annular space between the outsideperiphery of plate 384 at diameter D₃₈₄ and the inside wall of pipe 64or 78, in the radial direction, and by spaced pairs of ears 396 in thecircumferential direction. This gap, or set of gaps, or openings 400collectively from a passageway, or passageways, or a gallery ofpassageways through which the grey water may pass. The radial width, orradial extent, of such a gap 400 may be at least nominally taken asbeing the length of ears 396, indicated as h₃₉₆. The overall dimensionof the lower manifold assembly across ears 396 is shown as D₃₉₆. It isless than or equal to the overall diameter of the outer peripheral wall372 of upper manifold 356, and, where the external grey watercontainment shell employs pipe coupling 68, it is less than or equal tothe inside diameter of coupling 68, or, equivalently in practical terms,less than or equal to the outside diameter of the cut pipe of pipe 64 or78.

Lower manifold 358 may tend to obstruct the pathway for the flow of greywater. To provide a greater overall cross-sectional area for the greywater to pass with less obstruction, the spacing of the lower ends ofpipes 364 at plate 384 is tighter, or closer together, than the spacingat the top of pipes 364 at plate 368. This permits diameter D₃₈₄ to besmaller, and the size of gaps 400 to be relatively larger, thanotherwise. Toward this end, pipes 364 in the outer array could be set ona straight taper continuously from end to end. Alternatively, as shown,upper portions 402 of tubes 364 are parallel to the longitudinaldirection, and the lower portions 404 are angled inward, i.e., deviateradially inward. That is, pipes 364 are bent pipes, not straight pipes,there being a bend, or elbow, or kink between the upper and lowerportions as at 406, lower portion 404 being much shorter than upperportion 402. In the embodiment illustrated, lower portion 404 is roughly⅛ of the overall length of pipes 364, such that the majority, being thelarge majority, of each of pipes 364 extends at the larger radius R₃₆₄such as may tend to permit the flow of grey water more easily betweenand around pipes 364. This can be expressed in several ways. The pitchcircle of the lower grouping of pipe ends or fittings on radius R₃₉₄ issmaller than the pitch circle at the upper grouping of pipe fittings orends on radius R₃₆₄. Alternatively, if a periphery is drawn around thepipe ends, i.e., all of the pipes are circumscribed by the shortestexternal boundary line that can be drawn, the overall footprint area ofthe bottom ends of the pipe array is smaller than the correspondingfootprint at the top ends, although the total cross-sectional area ofpipes 364 is the same at both ends. The gap between pipes 364 and theoutside wall of return pipe 362 is smaller at the bottom than at thetop. As may be noted, the total cross-sectional area of the grey waterpath is greater than the total cross-sectional area of pipes 364. In theembodiment shown, the sum of the grey water area in gaps 400 is morethan double the internal area of the fresh water pipes 364.

In summary, assembly 360 is for use in a grey water heat recoveryapparatus and is installed in a shell, such as a plastic cylindricaltube or pipe to define a first heat exchanger pass for use in thevarious embodiments described above. The external shell may be pipe 64or 78. The pass has a tube bundle assembly, namely assembly 360. Theexternal shell can be formed of a cylindrical plastic pipe 64 or 78. Theexternal shell can also, alternatively, be formed of a mild steel orstainless steel pipe with a layer of thermal insulation, or a plasticpipe with an additional layer of thermal insulation. The cylindricalplastic pipe has a first end and a second end. In operation, the firstend is located higher than the second end—the grey water flow path is agravity flow conduit. The second end, i.e., the bottom end is blocked toform a sump within the cylindrical plastic pipe. The cylindrical plasticpipe has a first port and a second port; the first port is nearer thefirst end than is the second port. The first port defines a restingwater level when gray water is contained in the sump. Depending on whichway the pipe is connected, one of the first and second ports defines aninlet for grey water to the cylindrical plastic pipe, the other of thefirst and second ports defines the outlet for grey water from thecylindrical plastic pipe. Accordingly, the cylindrical plastic pipedefines a flow path for grey water between the inlet and the outletthereof. The first end of the cylindrical plastic pipe providing anentry, or entryway, into which to admit the lower end, and substantiallythe entire body of assembly 360, up to flange 374, which acts as a stopto locate assembly 360 longitudinally in its axially installed positionrelative to pipe 64 or 78 (or such other as may be). The tube bundle issized to fit within the entry at the first end of the plastic pipe. Theoutside peripheral cylindrical wall of the upper manifold is sized tonest with little or no slack or tolerance within the open end of pipe 64or 78. During installation the tube bundle is axially slidable withinthe external shell to reach the position dictated by the abutment offlange 374 with the cut end of pipe 64 or 78. The tube bundle has afirst end and a second end. The tube bundle has a first manifold 356 atthe first end (i.e., the upper or top end) thereof, and a secondmanifold 358 at the second end (i.e., the lower or bottom end) thereof.The tube bundle has a return, namely return pipe 362, passing throughfirst manifold 356, and extending to second manifold 358. First manifold356 and second manifold 358 fit within the cylindrical plastic pipe. Asinstalled, the second end (i.e., the bottom end) of the tube bundle iscloser to the second end (i.e., the bottom end) of the cylindricalplastic pipe than is the first end (i.e., the top end) of the tubebundle. The tube bundle has an inlet 92, and an outlet 98. The tubebundle defines a fresh water flow path between inlet 92 and outlet 98.Both inlet 92 and outlet 98 are located at the first end of the tubebundle. As installed in the cylindrical plastic pipe, the inlet and theoutlet of the tube bundle are accessible at the first end of thecylindrical plastic pipe at a level higher than the resting water levelof the cylindrical plastic pipe.

In that assembly, pipe 64 or 78 has at least one of (a) an insidediameter less than 8 inches (in the embodiment illustrated it may beabout 4″ i.d.); and (b) a length to diameter ratio of greater than 8:1.As illustrated in the previous embodiments, a counter-flow heatexchanger assembly may include two, three, or more such passes mountedside-by-side and joined together in fluid communication in series. Asshown in FIG. 8 and FIG. 9, first and second, or first second and thirdsuch heat recovery apparatus can be mounted together within a singlehousing, e.g., housing 128. It may include straight legs, or it mayinclude a set of helical coils extending around, i.e., wound around, thereturn pipe, 362. The second end of the cylindrical plastic pipe has avalve 76 mounted thereat. Valve 76 is operable to permit flushing of thesump, as, for example, when there is a sediment build-up in the bottom,as in a trap, or at any time that a filter may indicate that periodiccleaning may be advisable. As described, the grey water and fresh watersides of the apparatus are segregated. The fresh water side is typicallyat much higher pressure than the grey water side, such that any leak mayflow out of the fresh water side into the grey water side. In any case,the assembly may be given a non-electrically conductive coating, andleak detection sensors may be mounted, and monitored, such that theapparatus includes a leak detector. The return pipe is at leastpartially insulated, or isolated, and part of that insulation orisolation may be mounted in the annular gap between inner annular wall370 and pipe 362. The tube bundle includes an array of pipes 364 spacedabout return pipe 362. The array of pipes extends between, and is influid communication with, first manifold 356 and second manifold 358.The array of pipes has a tighter footprint at the second manifold thanat the first manifold. Alternatively expressed, the second manifold hasa smaller outside wall diameter of wall 388 than does the first manifoldat outer peripheral wall 372.

In that assembly, the grey water heat recovery apparatus has acylindrical plastic pipe and a tube bundle that inserts axially withinthe cylindrical plastic pipe. The tube bundle has a first manifold, asecond manifold, a return pipe, and a pipe array. The return pipe is influid communication with the second manifold and passes upwardly throughthe first manifold to terminate at a first pipe connection. The pipearray extends between, and is in fluid communication with, both thefirst manifold and the second manifold; the first manifold has a secondpipe connection extending upwardly therefrom, the second pipe connectionis in fluid communication with the first manifold. The pipe array has asmaller connection footprint with the second manifold than with thefirst manifold. The second manifold has a peripherally extending wall.The first manifold also has a peripheral wall. The peripheral wall ofthe second manifold has a shorter periphery than has the peripheral wallof the first manifold. Expressed differently, the pipe array has asmaller connection footprint with the second manifold than with thefirst manifold. The pipe array includes at least a first pipe that has astraight portion extending axially from the first manifold, and a bentportion extending from the straight portion toward the second manifold.In that array, the straight portion of the pipe is more than twice thelength of the bent portion (in the embodiment shown it is more than 7times the length of the bent portion, the straight portion being morethan ⅞ of the overall length). Alternatively expressed, the peripheralwall of the first manifold has a first diameter. The peripheral wall ofthe second manifold has a second diameter. The second diameter issmaller than the first diameter. In another feature, the second manifoldhas a set of centering ears extending radially outwardly thereof. Thegrey water flow path includes portions or passages defined outwardly ofthe second manifold, inwardly of the cylindrical plastic pipe, andsectorally between an adjacent pair of the centering ears. The pipearray has a total cross-sectional flow area that is at least as great asthe cross-sectional flow area of the return pipe.

What has been described above has been intended illustrative andnon-limiting and it will be understood by persons skilled in the artthat changes and modifications may be made without departing from thescope of the claims appended hereto, particularly in terms ofmixing-and-matching the features of the various embodiments as may besuitable. Various embodiments of the invention have been described indetail. Since changes in and or additions to the above-described bestmode may be made without departing from the nature, spirit or scope ofthe invention, the invention is not to be limited to those details butonly by a purposive reading of the appended claims as required by law.

We claim:
 1. A grey water heat recovery apparatus comprising: at least afirst heat exchanger pass having an external shell and a tube bundle;said external shell being formed of a cylindrical pipe; said cylindricalpipe having a first end and a second end; in operation, said first endbeing located higher than said second end; said second end being blockedto form a sump within said cylindrical pipe; said cylindrical pipehaving a first port and a second port; said first port being nearer saidfirst end than is said second port; said first port defining a restingwater level when gray water is contained in said sump; one of said firstand second ports defining an inlet for grey water to said cylindricalpipe, the other of said first and second ports defining an outlet forgrey water from said cylindrical pipe, said cylindrical pipe defining aflow path for grey water between said inlet and said outlet thereof;said first end of said cylindrical pipe providing an entry; said tubebundle being sized to fit within said entry at said first end of saidpipe; said tube bundle being axially slidable within said external shellon installation; said tube bundle having a first end and a second end;said tube bundle having a first manifold at said first end thereof, anda second manifold at said second end thereof; said tube bundle includinga return passing through said first manifold and extending to saidsecond manifold; said first manifold and said second manifold fittingwithin said cylindrical pipe; as installed, said second end of said tubebundle being closer to said second end of said cylindrical pipe than issaid first end of said tube bundle; said tube bundle having an inlet andan outlet, said tube bundle defining a fresh water flow path betweensaid inlet and outlet thereof; both said inlet and said outlet of saidtube bundle being located at said first end of said tube bundle; and asinstalled in said cylindrical pipe, said inlet and said outlet of saidtube bundle being accessible at said first end of said cylindrical pipeat a level higher than said resting water level of said cylindricalpipe.
 2. The grey water heat recovery apparatus of claim 1 wherein saidcylindrical pipe has at least one of (a) an inside diameter less than 8inches; and (b) a length to diameter ratio of greater than 8:1.
 3. Agrey water heat recovery apparatus comprising at least a first and asecond heat recovery apparatus of claim 1 mounted side-by-side andjoined together in fluid communication in series.
 4. The grey water heatrecovery apparatus of claim 3 wherein at least said first and secondheat recovery apparatus are mounted together within a single housing. 5.The grey water heat recovery apparatus of claim 1 wherein said tubebundle includes a set of helical coils extending around said return. 6.The grey water heat recovery apparatus of claim 1 wherein said secondend of said cylindrical pipe has a valve mounted thereat, and said valveis operable to permit flushing of said sump.
 7. The grey water heatrecovery apparatus of claim 1 wherein said apparatus includes a leakdetector.
 8. The grey water heat recovery apparatus of claim 1 whereinsaid return is at least partially insulated.
 9. The grey water heatrecovery apparatus of claim 1 wherein said tube bundle includes an arrayof pipes spaced about said return pipe; said array of pipes extendingbetween, and being in fluid communication with, said first manifold andsaid second manifold; said array of pipes has a tighter footprint atsaid second manifold than at said first manifold.
 10. The grey waterheat recovery apparatus of claim 1 wherein said second manifold has asmaller outside wall diameter than does said first manifold.
 11. A greywater heat recovery apparatus comprising: a pipe and a tube bundle thatinserts axially within said pipe; said tube bundle having a firstmanifold, a second manifold, a return pipe, and a pipe array; saidreturn pipe being in fluid communication with said second manifold andpassing upwardly through said first manifold to terminate at a firstpipe connection; said pipe array extending between, and being in fluidcommunication with both said first manifold and said second manifold;said first manifold having a second pipe connection extending upwardlytherefrom, said second pipe connection being in fluid communication withsaid first manifold; and, at least one of (a) said pipe array has asmaller connection footprint with said second manifold than with saidfirst manifold; and (b) said second manifold has a peripherallyextending wall, said first manifold has a peripheral wall, and saidperipheral wall of said second manifold has a shorter periphery than hassaid peripheral wall of said first manifold.
 12. The grey water heatrecovery apparatus of claim 11 wherein said pipe array has a smallerconnection footprint with said second manifold than with said firstmanifold.
 13. The grey water heat recovery apparatus of claim 11 whereinsaid second manifold has a peripherally extending wall, said firstmanifold has a peripheral wall, and said peripheral wall of said secondmanifold has a shorter periphery than has said peripheral wall of saidfirst manifold.
 14. The grey water heat recovery apparatus of claim 11wherein said pipe array includes at least a first pipe that has astraight portion extending axially from said first manifold, and a bentportion extending from said straight portion toward said secondmanifold.
 15. The grey water heat recovery apparatus of claim 14 whereinsaid straight portion is more than twice the length of said bentportion.
 16. The grey water heat recovery apparatus of claim 11 wherein:said peripheral wall of said first manifold has a first diameter; saidperipheral wall of said second manifold has a second diameter; and saidsecond diameter is smaller than said first diameter.
 17. The grey waterheat recovery apparatus of claim 11 wherein said second manifold has aset of centering ears extending radially outwardly thereof.
 18. The greywater heat recovery apparatus of claim 17 wherein a grey water flow pathis defined outwardly of said second manifold, inwardly of saidcylindrical pipe, and sectorally between an adjacent pair of saidcentering ears.
 19. The grey water heat recovery apparatus of claim 11wherein said pipe array has a total cross-sectional flow area that is atleast as great as the cross-sectional flow area of said return pipe. 20.The grey water heat recovery apparatus of claim 11 wherein: both of (a)said pipe array has a smaller connection footprint with said secondmanifold than with said first manifold; and (b) said second manifold hasa peripherally extending wall, said first manifold has a peripheralwall, and said peripheral wall of said second manifold has a shorterperiphery than has said peripheral wall of said first manifold; saidpipe array includes at least a first pipe that has a straight portionextending axially from said first manifold, and a bent portion extendingfrom said straight portion toward said second manifold; said straightportion is more than twice the length of said bent portion; saidperipheral wall of said first manifold has a first diameter; saidperipheral wall of said second manifold has a second diameter; saidsecond diameter is smaller than said first diameter; said secondmanifold has a set of centering ears extending radially outwardlythereof. a grey water flow passage is defined outwardly of said secondmanifold, inwardly of said cylindrical pipe, and sectorally between anadjacent pair of said centering ears ; and said pipe array has a totalcross-sectional flow area that is at least as great as thecross-sectional flow area of said return pipe.